i have submitted a site map for google what does it mean to google it is there are some 404 pages so,will google penalize my site for not building properly?
You can use some online tool to create your sitemap automatically - it spiders your web and create index of your pages. Using this way you will avoid 404 errors.
Notice though that Google may show 404 errors for URLs that your own website/sitemap have no references to. But indeed, if unsure, you should check using a link checker / website analyzer program that you don't have any internal broken links in your website.
Its seems mostly an eye soar in your webmaster tools. Google caches sitemaps and links so an old sitemap that included that link may be the cause. With time and a correct sitemap these warnings should disappear.